title: Are there sleep-specific phenotypes in patients with chronic fatigue syndrome? A cross-sectional polysomnography analysis.
abstract: OBJECTIVE
  Despite sleep disturbances being a central complaint in patients with chronic fatigue syndrome (CFS), evidence of objective sleep abnormalities from over 30 studies is inconsistent. The present study aimed to identify whether sleep-specific phenotypes exist in CFS and explore objective characteristics that could differentiate phenotypes, while also being relevant to routine clinical practice.
  
  
  METHODS
  A cross-sectional, single-site study.
  
  
  METHODS
  A fatigue clinic in the Netherlands.
  
  
  METHODS
  A consecutive series of 343 patients meeting the criteria for CFS, according to the Fukuda definition.
  
  
  METHODS
  Patients underwent a single night of polysomnography (all-night recording of EEG, electromyography, electrooculography, ECG and respiration) that was hand-scored by a researcher blind to diagnosis and patient history.
  
  
  RESULTS
  Of the 343 patients, 104 (30.3%) were identified with a Primary Sleep Disorder explaining their diagnosis. A hierarchical cluster analysis on the remaining 239 patients resulted in four sleep phenotypes being identified at saturation. Of the 239 patients, 89.1% met quantitative criteria for at least one objective sleep problem. A one-way analysis of variance confirmed distinct sleep profiles for each sleep phenotype. Relatively longer sleep onset latencies, longer Rapid Eye Movement (REM) latencies and smaller percentages of both stage 2 and REM characterised the first phenotype. The second phenotype was characterised by more frequent arousals per hour. The third phenotype was characterised by a longer Total Sleep Time, shorter REM Latencies, and a higher percentage of REM and lower percentage of wake time. The final phenotype had the shortest Total Sleep Time and the highest percentage of wake time and wake after sleep onset.
  
  
  CONCLUSIONS
  The results highlight the need to routinely screen for Primary Sleep Disorders in clinical practice and tailor sleep interventions, based on phenotype, to patients presenting with CFS. The results are discussed in terms of matching patients' self-reported sleep to these phenotypes in clinical practice.
authors.affiliation: Northumbria Centre for Sleep Research, Department of Psychology, Northumbria University, Newcastle, UK.
authors.forename: Zoe M
authors.initials: ZM
authors.lastname: Gotts
authors.forename: Vincent
authors.initials: V
authors.lastname: Deary
authors.forename: Julia
authors.initials: J
authors.lastname: Newton
authors.forename: Donna
authors.initials: D
authors.lastname: Van der Dussen
authors.forename: Pierre
authors.initials: P
authors.lastname: De Roy
authors.forename: Jason G
authors.initials: JG
authors.lastname: Ellis
keywords: Internal Medicine; Mental Health; Sleep Medicine; Statistics & Research Methods